This invention concerns an apparatus for the production of molded articles made of plastic or rubber in at least one molding station having at least one mold consisting of upper and lower halves clamped together in the closed position by means of elastic elements.
In die casting, injection molding and vulcanization machines large hydraulic cylinders are usually assigned to each molding station to transfer comparatively high closing forces to the mold parts. In addition, the individual molding stations are often equipped with separate, long-stroke transport cylinders which execute the opening movements of the mold parts when the closing cylinder is relieved. Such devices are expensive to construct and maintain owing to the large number of pressure cylinders, particularly when the device has a great number of molding stations - for example on a turntable.
A known apparatus for a single molding station presses together the two halves of the mold with a preloaded spiral spring acting against the upper half of the mold in its closed position. This spring rests at one end on the upper side of the mold half and at the other end on the head of a threaded pin for adjusting the tension force. The opening of the mold is effected by a pressure cylinder against the closing force of the spring, i.e. by further compressing it (German Pat. No. 2,052,177). This device is still comparatively complex, and the structural design of the molding station results in an unbalanced distribution of the closing forces. Finally, it is a disadvantage that when the mold is open the spring is permanently subjected to an increased tension.